Patent GB-655883-A (GB)
Title: Improvements in or relating to gear mechanisms
IPC: F16H61/02
Filed: 1948-03-05
Abstract: 655,883. Change-speed control; friction clutches. CAMPBELL & ISHERWOOD, Ltd., and MEREDITH, J. March 5, 1948, No. 6845. [Class 80(ii)] Relates to gearing which changes from one speed ratio to another after a predetermined period, as by changing-up a certain time after starting, through the action of yielding means responsive to the operation of the one ratio, and comprises a hydraulic system transfer of liquid in which by the yielding means actuates, or allows actuation of, the appropriate ratio change. As shown, applied to the drive from an electric motor to a coal conveyer, the planets 16; Fig 3, of a carrier 15 fast with the driven shaft 13 mesh a driving sun 14 and a reaction annulus 17 held when drive commences by the appropriate one of two oppositely-acting pawls 20, Fig. 4, co-acting with a toothed drum 19 rigid with the annulus, and mounted on links 23 resiliently supoprted by springs 35. This affords a planetary reduction ratio, but the operative pawl 20 yields gradually under the reaction torque, at first to take up lost motion in a pin and slot connection 28, 30 and. disengage completely the opposite pawl through a linkage 31, 33, and then to press back a piston 25 to transfer oil from the cylinder 26 through an adjustable restriction valve (not shown) to a cylinder 36 controlling the engagement of a multiplate direct-drive clutch 18, Fig. 3, between the annulus 17 and carrier 15. The clutch 18 is engaged, when locking levers 47 actuated from the cylinder 36 are withdrawn by weights 48 sliding centrifugally outwards against spring loading to expand a toggle 59 through a resilient connection 49. The levers 47 are withdrawn by a sliding shaft 44 connected by a pin 42, passing through a slot in the driven shaft 13, with a collar 40 actuated by a yoke 38, Fig. 4, operated with an adjustable lost motion take-up by a rock shaft 39 fast with arms 37 connected to the piston of the cylinder 36. The clutch 18 is therefore engaged at a given time, say between one and thirty minutes according to the setting of the restriction valve, after the commencement of drive, providing the motor speed is high enough; and direct drive then persists until, as on stoppage of the motor, the speed decreases sufficiently for the weights 48 to be moved inwardly. The weights co-act with nose portions on the levers 47 through rollers 55 and, once the rollers have passed inwardly over these portions, the clutch 18 is rapidly disengaged and the rest of the operating mechanism returns to its starting position under the action of a spring in the cylinder 36. The drive is then again in reduced ratio ready for another sequence of operations. During direct drive, both pawls 20 are held positively out of contact with the drum 19 by arms 51 which have cams engaging extensions 52 on the pawls and are operated through springs 53 by the rock shaft 39. In a diagrammatic modification, Figs. 1 and 2 (not shown), the whole annulus is slidden axially to engage a clutch surface on the planet carrier, and there may be only a single reaction pawl so that the drive is only operative in one direction of rotation. Specifications 630,512, [Group XXX], and 636,404 are referred to.